The robbery occurred shortly after 9:05 a.m. near the intersection of Washington and Liberty streets, according to police.
A female victim was walking to her vehicle with her wallet in her hand when a man approached her, grabbed her wallet, and knocked her to the ground, police said.
The victim chased the suspect, who got into a vehicle driven by a female suspect. The vehicle was last seen traveling east on Washington Street, according to police.
The suspect who grabbed the wallet from the victim is described as a black man in his 20s who is thin and has dreadlocks. The driver is described as a black woman in her 20s with braids in her hair, police said.
The victim suffered a minor abrasion to her hand, but it did not need treatment.
Anyone with information about the incident is asked to call Petaluma police Officer Parnow at (707) 778-4372.